VALIDITY OF RISK GROUP DEFINITION IN DIFFERENTIATED THYROID-CARCINOMA

Despite the usual excellent prognosis of differentiated thyroid carcin oma, some patients die because of disease. It has been speculated that lethal disease may have a better prognosis if patients are treated wi th extensive surgery plus I-131 ablative treatment. We have analyzed a group of 223 patients with differentiated thyroid carcinoma treated u nder a uniform therapeutic protocol of surgery and followed for 3 to 1 7.7 years, in order to differentiate patients with a high and a low ri sk of mortality and the influence of therapy on survival rate. The the rapeutic protocol was as follows. If the diagnosis was papillary carci noma, subtotal thyroidectomy was performed and cervical nodes were rem oved if they were suspicious for cancer. If the diagnosis was follicul ar carcinoma, a total thyroidectomy was performed. I-131 was given in cases of patients who were more than 60 years old or who had extrathyr oid disease or metastases in papillary carcinomas and in macroangioinv asive follicular carcinomas. In survival analysis, the event used as t he end-point was death due to thyroid carcinoma and summarized by the Kaplan-Meier curve and the Mantel-Cox method. We found three independe nt prognostic factors which determined mortality: over 60 years of age , tumor size larger than 6 cm and metastases. On the basis of these fa ctors we identified two risk groups: a low-risk group (A), who had no risk factors, composed of 153 patients whose survival rate at 205 mont hs was 100% and a high-risk group (6), who had one or more risk factor s, composed of 55 patients whose survival rate at 213 months was 39.6% . Seventeen patients in this second group died from thyroid carcinoma. We therefore analyzed the effect of treatment in group B. Patients wh o had more extensive surgery had a similar survival rate to those who had less extensive surgery and I-131 administration did not modify the survival rate. These data support the idea that the identification of low-risk groups may facilitate a more rational approach to treatment of differentiated thyroid carcinoma, avoiding aggressive therapy in ca ses with a good prognosis.